The major objectives of the proposed research are to: revise the model we have previously developed to incorporate recent advances in knowledge of the epidemiology of HIV/AIDS and changes introduced by both drug prophylaxis/treatment and behavioral change; use the model to explore and expand our understanding of the natural history of HIV/AIDS with particular emphasis on establishing rate of disease progression in IVDUs; and perform a set of policy analyses that would allow HIV prevention approaches to be evaluated in the context of drug treatment and/or HIV counseling programs. Recent use of antivirals and prophylactic measures have altered the incubation and survival functions--crucial parameters for any model that will be used for forecasting HIV and AIDS prevalence. Using data which have become available from the National Institute of Allergies and Infectious Diseases (NIAID) under the AIDS Clinical Trials Coordinating Center project, we propose to revise these parameters and make short-term forecasts of HIV seroprevalence and AIDS incidence. Two other sources of data are NIDA's AIDS Targeted Outreach Program and CDC's HIV counseling and Treatment Evaluation Study. Interventions under these program will yield data on changes in drug-use behavior and sexual practices. These changes are especially relevant for intravenous drug abusers. When details on drug abuse behavior are supplied to the revised model, the effect of various intervention strategies on the current epidermic will be evaluated. The HIV/AIDS prevalence model developed by RTI includes the following characteristics: all primary risk groups are represented; risk group size is based on AIDS incidence data that accounts for risk behaviors, thereby estimating only those with high risk behaviors; and contacts that result in infection are treated as endogenous model parameters so that changes in risk group behavior are implicitly measured. As a result, the model avoids the pitfalls of many of the models reported in the literature that treat contact rate a known exogenous parameters.